Seeing the reactions this is getting from all of you, I have to wonder if this was not some sort of PR stunt after all... if some guy with a degree in marketing prepared the iPod and trained the President how to pronounce all the proper names. The President still mispronounced some of them, though.

If they were Iraqi baby seals, yes.
I don't know if there's any hard and fast rule about bands in general, but they're certainly categorized as 'artists' for indexing and reference purposes. And the Beatles were the best as far as I'm concerned. By that, I mean that if I could only listen to one artist for the rest of my life, there's no question that I would choose them. You can't possibly get bored of a selection that ranges from 'She Loves You' through 'Come Together' to 'Fool on the Hill'. Their variety was incredible. That's one reason why I also love Elton John's stuff.